I have quite a few questions (in bold text) in order to narrow down where in the Evap system is causing the P0455 code. Please feel free to respond if you can answer only one of my questions. Any response is appreciated.

Check Engine light gives fault code P0455: Evaporative Emission Control System Leak Detected (gross leak, check fuel cap, piping etc). Also car had rough idling. Now, diagnosis:

I apply voltage to the Evap purge valve but it does not make any clicking noise. So I ordered a new one which does sound a click when applied voltage. The new part came exactly like in the picture below, notice the black cap below the electrical connector that can be removed exposing a tube underneath.
enter image description here

There is a difference where this cap is fit on on the old valve: enter image description here

So I pull out the black cap on the new valve and install exactly like the old valve, clear fault code. Drove for a week, I think rough idling is gone. The other day when accelerating on high way, check engine light came back on again. Still same code P0455. I just got this car, so I'm not sure if it is because Q1: the old valve had always been installed wrong or not?

I also see there are 2 same valves in the picture below that its black cap is fit on below the electrical connector. Q2: What are these 2 valves?
enter image description here

Next step would be removing the Evap vent valve, then apply voltage to check, but it is currently out of stock on Rockauto. Q3: Does anybody know if I can replace with a similar part from another model or vehicle?

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